Technetium-99m-pertechnetate as a whole blood marker for brain perfusion studies

J Nucl Med. 1994 Mar;35(3):479-83.

Abstract

In the brain, diffusible 99mTc-pertechnetate behaves as an intravascular indicator because it is confined within the circulation by the blood-brain barrier, allowing its use for noninvasive dynamic evaluation of cerebral circulation. For this application 99mTc has often been claimed to be a plasma marker. This study examines the validity of such a claim which has not yet been proven in vivo.

Methods: The relative amount of 99mTc in the red cells circulating in large vessels was compared to the corresponding hematocrit (LV Hct) during the rapid (t/2 = 1.98 min) and slow (t/2 = 84 min) phases of 99mTc disappearance from the circulation after bolus intravenous injection. These comparisons were performed on rats at 2 (n = 3), 5 (n = 6), 10 (n = 6) and 20 (n = 9) sec after intravenous injection for the rapid phase and 5 (n = 5), 30 (n = 4), 60 (n = 6) and 120 (n = 6) min after intravenous injection for the slow phase.

Results: The results show that the relative amount of intravascular 99mTc fixed to red cells did not differ statistically from LV Hct until at least 1 hr after intravenous administration. This homogeneous distribution of 99mTc in blood was indisputable during the first 20 sec but became progressively less evident and disappeared after 2 hr. Such behavior was attributed to a progressive increase of free 99mTc, which, in whole blood, amounted to 4% at 20 sec and 25% at 2 hr after injection.

Conclusion: Because it is a 96% whole blood marker early after intravenous administration, 99mTc is a reliable agent for first-pass studies of whole blood circulation in the brain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / diagnostic imaging*
  • Cerebrovascular Circulation / physiology*
  • Erythrocytes*
  • Female
  • Hematocrit
  • Radionuclide Imaging
  • Rats
  • Rats, Sprague-Dawley
  • Sodium Pertechnetate Tc 99m*

Substances

  • Sodium Pertechnetate Tc 99m